The present invention relates to a transducer to detect a cutting force or cutting resistance which is applied to a machine tool when machining a workpiece and, more particularly, to a transducer to detect a cutting force or cutting resistance by using a piezoelectric sensor and to attaching structure which attaches such a transducer to a machine tool.
In recent years, in association with the practical use of production systems such as FMC, FMS, or the like, a machine tool such as a machining center, NC lathe, or the like has been operated in an automatic manner. In the automatic operation, an in-process monitoring of the cutting state is very desirable to detect the occurrence of an abnormality during the machining of a workpiece. In particular, the measurement of the cutting force and cutting resistance which can indicate such an abnormality is used as such a process.
Hitherto, to measure the cutting force or cutting resistance, methods in which a strain gauge or quartz resonator is assembled in a tool or the like and strain is measured and in which a load current of a motor to drive the main shaft is measured, have been employed.
However, in the strain measuring method, the detector is expensive and the rigidity of the detector itself is low, so that when a large force is applied to the detector, it is easily broken. On the other hand, in the strain measuring method or the motor load current measuring method, when measuring a small cutting force or cutting resistance of a small-diameter drill, a tap, or the like, since the detection sensitivity is so low the detector is influenced by noise or the like. Thus, it is difficult to accurately measure the cutting force or cutting resistance. Such a problem is a large obstacle in carrying out the automatic operation of the machine tool.